1. Field of the Invention
The present invention relates to an image forming apparatus.
2. Description of the Related Art
In the specification of Japanese Patent No. 2858441, an image forming apparatus is proposed that detects a jam generated when a recording material unintentionally wraps around a fixing unit.
Specifically, in this image forming apparatus, sensors for detecting the recording material are provided on an upstream side and a downstream side relative to the fixing unit in a conveyance direction of the recording material. Using these two sensors, the image forming apparatus determines that a jam in which the recording material wraps around the fixing unit has been generated when, while the upstream-side sensor is detecting the recording material, the downstream-side sensor changes from a state of detecting the recording material to a state of not detecting the recording material before passage of a predetermined time period in which a trailing edge of the recording material is expected to pass the downstream-side sensor.
However, in the above conventional technology, there are the problems described below. For example, an image forming apparatus sometimes has a configuration whereby there is a difference between an interval from the trailing edge of a preceding recording material to the leading edge of a subsequent recording material (referred to below as an interval between papers) that can be detected by the sensor on the upstream side in the conveyance direction relative to the fixing unit, and an interval between papers that can be detected by the sensor on the downstream side in the conveyance direction. In particular, in image forming apparatuses, there has recently been a tendency to set a shorter interval between papers than in the prior technology in order to improve throughput. In such a case, when an interval between papers fails to be detected with an upstream-side registration sensor for detecting recording material that has been fed, but the interval between papers is detected with a discharge sensor on the downstream side for detecting that recording material has been discharged outside of the image forming apparatus, there is a possibility that even though the recording material is being conveyed normally with a short interval between papers, it may be incorrectly judged that a jam in which recording paper wraps around the fixing unit has been generated.